Now look at the specs in the online manual (and I would imagine the printed manual as well) for the MGA amplifiers.

2.
Better support for older/discontinued SAS equipment (archived online manuals/specs). You have online support (manuals/specs) for the ELA series amps, but nothing for the RS series amps (which are a lot "newer")? Nothing for the older EL series subs, or any of the RS series subs (except the RSW series).